Recently, copper alloy netting has been proposed as a material for aquaculture facilities that can be set in harsh offshore environments. To design a cage made of copper alloy netting, it is necessary to calculate the flow of water through the netting and force of external sources on the netting. Therefore, this study measured and analyzed the current velocity reduction after passing through the netting and the hydrodynamic forces acting on the netting using copper alloy netting with nine solidity ratios. As a result of the reduction rate of the flow velocity through the netting, the flow reduction rate was increased as the solidity ratio of netting was increased. The flow reduction rate was also increased as the attack angle on the netting was decreased. In analyzing the resistance on the netting, we also discovered that resistance was increased with increase in the flow velocity and solidity ratio. An analysis of the hydrodynamic coefficient acting on the netting is shown that the drag coefficient tends to increase as the attack angle increases. We also analyzed the hydrodynamic coefficient according to the variation of the Reynolds number. When the drag coefficients acting on the netting were analyzed with the different Reynolds numbers, the Reynolds number increased from over 0.3 m/s to a relative constant. Finally, the copper alloy nettings had a smaller velocity reduction rate when comparing the flow velocity reduction rate between copper alloy nettings and nylon nettings.

Vortex tubes are simple tubes that can separate hot and cold air from compressed air without any internal device configuration and are used in many industries. If the vortex tube with these advantages is applied to an air conditioning system, it will be free from the use of refrigerant. In this study, basic study on discharge flow rate and temperature separation characteristics was carried out by varying the number of generator nozzle hole in various shapes of the vortex tube according to the inlet pressure of the vortex tube. Experimental results show that as the number of nozzles increases, the discharge flow rate tends to decrease and the temperature separation characteristics were excellent in the number of nozzles 6~7.

Numerical analysis has been carried out to investigate seawater flow field characteristics with various current directions near the manganese nodule mining device. Seawater flow near the collecting device is largely influenced by the sea current direction, especially along the downstream of the rear system. Predicted flow velocity distributions are analyzed with turbulent kinetic energy and drag force. There is big flow field variation when the direction angle between the mining device and seawater current flow approaches to 30°~ 120°, and flow velocity along the rear region of 60° becomes faster than 180°. Averaged turbulent kinetic energy at 180° also becomes low, about 57% higher at 60°. These results from the study can be applicable to the optimum design of manganese nodule collecting system in the deep seawater flow.

국내 가동원전 중 2-루프 가압경수로인 고리1호기는 약 40년 운전한 후, 2017년 6월 18일 영구정지되었다. 영구정지된 고리 1호기는 주요 해체작업을 수행하기전에 계통내 선량률을 저감시켜 작업자피폭을 최소화하기 위한 계통제염을 수행할 예정이다. 일반적으로, 계통제염 범위는 원자로압력용기, 가압기, 증기발생기, 화학 및 체적제어계통, 잔열제거계통 및 원자로 냉각재계통 주요배관을 포함한다. 이러한 계통 및 기기 등을 효율적으로 제염하기 위해서는 제염과정에서 원자로냉각재계 통내 유동특성을 평가할 필요가 있다. 계통제염을 위해 순환유량을 제공하는 방법은 다양하나, 본 논문에서는 잔열제거펌프 운전에 따른 고리1호기 원자로냉각재계통내 유동특성을 평가하였다. 잔열제거펌프를 이용한 계통제염은 원자로냉각재 내 유량의 불균형을 초래하여 계통내 기기 및 배관 등에 불순물을 침적시켜 제염이 효율적이지 않다는 것으로 평가되었다.

선박의 고속, 대형화 및 규제강화의 추세에 따라 유동소음의 중요성이 강조되고 있다. 그러나 항공, 철도 등의 공력소음 분야에서 유동소음을 설계에 반영하고 있는 것에 반해 조선해양분야에서는 고려되지 않고 있다. 본 연구에서는, 선체유기 유동소음의 해석절차를 정립하고 쇄파의 영향이 작고 선체선형에 의한 유기소음의 특성이 뚜렷한 파랑관통형 선형에 대해 소음특성을 분석하였다. 선체유기 유동소음의 주요 메커니즘인 난류경계층 내부의 복잡한 난류유동과 구조물의 유체-구조 연성적 소음원은 벽면변동압력을 이용하여 가진력을 모델링하고 파워흐름해석법을 이용하여 진동음향 응답해석을 수행하였다. 주파수 영역 및 선체부위에 따라 상의한 소음특성을 가지며 저주파수 영역에서 선형의 영향이 상대적으로 크고 유속에 비례하는 경향을 확인할 수 있었다.

본 연구에서는 이수의 유동 특성을 분석하기 위한 기초 연구로서 상용 코드인 ANSYS CFX 14.5를 이용하여 고체-액체 2상 유동 에 대한 수치해석적 연구를 수행하였다. 고체-액체 2상 유동 현상을 모사하기 위해서 균질류 모델과 분리류 모델을 사용하였다. 분리류 모델에서는 Gidaspow의 항력모델을 적용하였으며, 고체 입자에 운동 이론 모델을 적용하였다. 기존의 실험 결과를 기반으로 본 연구에서 사용한 수치해석 모델의 유효성을 검토하였으며, 수치해석은 직경 54.9 mm, 길이 3 m의 수평관에서 체적 분율 0.1~0.5, 속도 1~5 m/s 범위에서 수행되었다. 그리고 압력강하와 고체 입자의 체적 분율 분포를 확인하였으며, 압력강하는 균질류 모델과 분리류 모델이 각각 MAE 17.04%, 8.98 % 이내에서 실험결과를 잘 예측하였다. 관의 하부에서 높은 체적 분율이 나타나며, 상부로 갈수록 체적 분율은 감소하였다. 그리고 속도가 증가할수록 높이 변화에 따른 체적 분율 분포의 변화는 감소하였으며, 수치해석 결과는 이러한 유동 특성을 잘 예측하였다.

It is known that the cooling performance can be improved about 5~12% and the COP (Coefficient of Performance) can be improved about 10~15% when the IHX (Internal Heat Exchanger) was applied in a vehicle. Thus, the aim of this study was to observe the influence of the fins shape on the turbulence flow and turbulence kinetic energy gradient in IHX. All the applied parameters of the fin such as rotation angle, spacing ratio, height ratio and mass flow rate are changed. The governing equations for the flow motion simulation were applied to continuity equation and Navier-Stokes equation, and the turbulence model was applied by the Shear Stress Transport(SST) model, which has the advantage of turbulence simulation. As the rotation angles of the front and back fins were increased, the difference in the maximum turbulent kinetic energy gradient between fins was reduced. As the inlet flow mass increased, the turbulent kinetic energy difference between front and back fins were increased. The turbulence area tended to increase with increasing fin height ratio.

In this study, the CFD analysis was performed by changing the geometry of coil-tube diameter ratio, coil winding number, coil pitch, and cross section of the tube to investigate the heat flow characteristics of forced convection in a helical coil-tube heat exchanger using RSM (Reynolds Stress Model). As a result, the secondary flow was developed in the tube caused by the influence of centrifugal force. It improved the heat transfer on the outer side of the tube, but on the inner side was not performed well. And the temperature rose locally in the tube region. Also the pressure drop in the tube was proportional to the diameter ratio of the coil-tube and the inlet velocity, and it was found that pressure drop and friction factor were inversely proportional. When the coil winding number and coil pitch were increased, it affected heat transfer in the low speed range of 0.1 ~ 0.2 m/s, but did not affect the flow condition after this range.

경상북도 봉화군 토석류 발생지 40개소를 대상지로 선정하여 강우의 특성 및 다양한 산림환경인자 별 로 조사하여 토석류발생 특성을 분석하였다. 토석류 발생 수는 총 40개소였으며, 토석류 발생 평균 발생 면적은 1,614.1㎡, 평균 발생토사량은 2,450㎥, 평균 길이는 120.7m, 평균 폭 11.8m로 나타났다. 토석류 가 비교적 많이 발생한 산림환경인자는 사면경사도(41°이상), 북서사면, 해발(401m~500m 이하), 종단사면 (복합), 횡단사면(오목), 침엽수, 변성암, 하천차수는(0차), 사면위치(산복), 임종(인공림), 수고(11m~15m), 흉고직경은 중경목(17cm 이상)에서 나타났다. 토석류 발생길이와 산림환경인자와의 상관분석을 실시한 결과는 사면경사(31°~40°), 종단사면(복합) 횡단사면(오목) 에서 1% 수준 내에서 정의 상관관계를 보였 고, 사면경사(41°이상), 종단사면(직선)에서 1% 수준 내에서 부의 상관관계를 보였다.

It is necessary to develop a device for the design of wet scrubber with a more efficient deodorization performance in order to enhance the odor reducing effect of the wet scrubber. Therefore in this study, the superiority of the new wet scrubber with the centrifugal separation function different from the conventional wet scrubber was analyzed by the computational fluid dynamics. From CFD analysis, the pressure and velocity distribution, the peak vorticity, the retention time and the flow uniformity were calculated and compared with the performance characteristics of the centrifugal separator. As the results of CFD analysis, the peak vorticity and retention time of the gas flow were increased about 22% and the flow uniformity was improved about 7.2% by the centrifugal separator. Therefore the centrifugal separator in the wet scrubber will improve the deodorizing effect and the cleaning condition of the gas.

In this study, the heat flow characteristics of wave heat exchanger was investigated by being applied to the white smoke reduction system. Through numerical analysis, the heat transfer and flow characteristics of the wave heat exchanger with the change of inlet condition of air-side and water-side were analyzed. To investigate the temperature, the absolute humidity, heat transfer rate, pressure drop and turbulence characteristics of the wave heat exchanger, the simulation analysis was conducted by using the commercial computational fluid dynamics software (Solidworks Flow Simulation) under uniform flow conditions. As the inflow rate of air decreased and the inflow temperature of water increased, the heat transfer coefficient of the wave heat exchanger decreased. When the experimental conditions of water-side were the same, the air outlet temperature and absolute humidity of the wave heat exchanger increased with increasing inflow rate of air. To reduce the white smoke, the air outlet temperature and absolute humidity of the wave heat exchanger must be reduced. Therefore, the lower the air velocity and the water inflow temperature into the wave heat exchanger, the more effective it is.

According to the structure, solenoid valve can be categorized as spool valve or poppet valve. While various research on spool valve which has simple structure and fine susceptibility to contamination has been conducted, poppet valve which has less susceptibility to contamination and advantage in a long time operation still need much research because of its complicated structure. In order to design the poppet valve, various parameters such as the diameter of the poppet, the angle of the poppet, the diameter of the disk, the spring stiffness, the spring preload and flow path structure should be considered. Conventional studies on poppet valve usually take only one design parameters and did not much focused on the effect of the parameters on flow characteristics. In this paper, the change of the flow characteristics according to the design parameters of the poppet valve for 3/2Way solenoid valve is analyzed. The previous studies and the results of initial model analysis was referred for the selection of the design parameters. The effects of design parameters on maximum pressure, minimum pressure, and pressure drop was examined using analysis of means(ANOM).